Noise reduction system for composite structures

ABSTRACT

A method and apparatus comprising a composite panel and a number of structures to reduce noise radiation from the composite panel. The composite panel has a first face sheet, a second face sheet, and a core located between the first face sheet and the second face sheet. The number of structures is associated with the first face sheet. The number of structures has a mass with a configuration to reduce a speed of waves propagating in the composite panel such that noise radiating from the composite panel is reduced.

BACKGROUND INFORMATION

1. Field:

The present disclosure relates generally to aircraft structures and, inparticular, to aircraft using composite structures. Still moreparticularly, the present disclosure relates to a method and apparatusfor reducing noise in composite structures in an aircraft.

2. Background:

Aircraft are being designed and manufactured with greater and greaterpercentages of composite materials. For example, some aircraft may havemore than 50 percent of their primary structures made from compositematerials. Further, composite materials also may be used in the interiorof the aircraft and for other structures.

Composite materials are used in aircraft to decrease the weight of theaircraft. With the decreased weight, improved payload capacities andfuel efficiencies may occur. Further, composite materials also mayprovide a longer service life for various components in an aircraft.

Composite materials have a lighter weight and greater stiffness ascompared to metallic structures. As a result, composite materials alsoare more efficient in radiating noise as compared to metallic materials.With the use of composite materials in place of metallic materials,noise in the interior of an aircraft may be greater than desired.

Currently, noise is controlled using different types of noise reductionsystems. For example, dampening systems, fiberglass blankets, acousticfoam, isolators, and other systems may be used to reduce the noisegenerated by composite structures. These noise reduction systems,however, may be labor intensive for installation and may requireadditional space. Further, these types of systems also may be moreexpensive and add more weight than desired. Further, even with thesenoise reduction systems in place, the amount of noise reduction achievedmay not be as great as desired.

Therefore, it would be desirable to have a method and apparatus thattakes into account at least some of the issues discussed above as wellas possibly other issues.

SUMMARY

In one illustrative embodiment, an apparatus comprises a composite paneland a number of structures. The composite panel has a first face sheet,a second face sheet, and a core located between the first face sheet andthe second face sheet. The number of structures is associated with thefirst face sheet. The number of structures has a mass with aconfiguration to reduce a speed of waves propagating in the compositepanel such that noise radiating from the composite panel is reduced.

In another illustrative embodiment, a method for reducing noise ispresent. The method causes waves to propagate through a composite panelcomprising a first face sheet, a second face sheet, and a core locatedbetween the first face sheet and the second face sheet. A speed of wavespropagating through the composite panel is reduced with a number ofstructures associated with the first face sheet. The number ofstructures has a mass with a configuration to reduce the speed of thewaves propagating in the composite panel such that noise radiating fromthe composite panel is reduced.

The features and functions can be achieved independently in variousembodiments of the present disclosure or may be combined in yet otherembodiments in which further details can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives thereof will best be understood by reference to the followingdetailed description of an illustrative embodiment of the presentdisclosure when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is an illustration of an aircraft in which an illustrativeembodiment may be implemented;

FIG. 2 is an illustration of a composite structure that can be used witha noise reduction system in accordance with an illustrative embodiment;

FIG. 3 is an illustration of a cross-sectional view of a composite panelin accordance with an illustrative embodiment;

FIG. 4 is an illustration of a composite structure with a noisereduction system in accordance with an illustrative embodiment;

FIG. 5 is an illustration of a cross-sectional view of a composite panelin accordance with an illustrative embodiment;

FIG. 6 is an illustration of a composite structure with a noisereduction system in accordance with an illustrative embodiment;

FIG. 7 is an illustration of a cross-sectional view of a compositestructure with a noise reduction system in accordance with anillustrative embodiment;

FIG. 8 is an illustration of a composite structure with a noisereduction system in accordance with an illustrative embodiment;

FIG. 9 is an illustration of a cross-sectional view of a composite panelin accordance with an illustrative embodiment;

FIG. 10 is an illustration of a composite structure in accordance withan illustrative embodiment;

FIG. 11 is an illustration of a cross-sectional view of a compositestructure in accordance with an illustrative embodiment;

FIG. 12 is an illustration of a design environment for designing noisereduction systems for composite structures in accordance with anillustrative embodiment;

FIG. 13 is an illustration of a flowchart of a process for reducingnoise in accordance with an illustrative embodiment;

FIG. 14 is an illustration of a graph of noise reduction results inaccordance with an illustrative embodiment;

FIG. 15 is an illustration of a data processing system in accordancewith an illustrative embodiment;

FIG. 16 is an illustration of an aircraft manufacturing and servicemethod in accordance with an illustrative embodiment; and

FIG. 17 is an illustration of an aircraft in which an illustrativeembodiment may be implemented.

DETAILED DESCRIPTION

With reference now to the figures and, in particular, with reference toFIG. 1, an illustration of an aircraft is depicted in which anillustrative embodiment may be implemented. Aircraft 100 is an exampleof an aircraft in which noise reduction systems may be implemented inaccordance with an illustrative embodiment.

In the illustrative example, aircraft 100 has wing 102 and wing 104attached to fuselage 106. Aircraft 100 also includes engine 108connected to wing 102 and engine 110 connected to wing 104. Aircraft 100also has horizontal stabilizer 112, non-vertical stabilizer 114, andvertical stabilizer 115.

In these illustrative examples, noise reduction systems may beimplemented in or with various composite components in aircraft 100. Forexample, a noise reduction system may be implemented in a compositepanel for use within aircraft 100.

As depicted, an exposed view of interior 116 of aircraft 100 is shown.Within interior 116, one or more composite panels with a noise reductionsystem may be implemented. For example, a composite panel may beimplemented in wall 118 of closet 120. As another illustrative example,a composite panel with a noise reduction system may be implemented inceiling panel 122. As another illustrative example, a composite panelwith a noise reduction system may be implemented in floor panel 124.Composite panels with noise reduction systems in accordance with anillustrative embodiment may be implemented in still other structureswithin aircraft 100 in these illustrative examples.

The noise reduction system implemented in a composite panel for aircraft100 may reduce noise more efficiently than currently used noisereduction systems. Further, the weight of and space used by the noisereduction system may be less than those of currently available noisereduction systems.

With reference now to FIG. 2, an illustration of a composite structurethat can be used with a noise reduction system is depicted in accordancewith an illustrative embodiment. Composite structure 200 is an exampleof a composite structure that may be used in aircraft 100 in FIG. 1.

In this illustrative example, composite structure 200 takes the form ofcomposite panel 202. Composite panel 202 is a panel that may be usedwithin aircraft 100 in FIG. 1. For example, without limitation,composite panel 202 may be used for a wall of a closet, a ceiling panel,as part of a floor structure, or some other suitable structure withinaircraft 100.

As depicted, composite panel 202 comprises first face sheet 204 andsecond face sheet 206. Core 208 is located between first face sheet 204and second face sheet 206. In these illustrative examples, first facesheet 204 and second face sheet 206 may be stiffer than core 208.Further, core 208 may be weaker than first face sheet 204 and secondface sheet 206.

In this illustrative example, number of structures 210 in noisereduction system 211 is associated with first face sheet 204. In thisillustrative example, number of structures 210 takes the form of layer212.

When one component is “associated” with another component, theassociation is a physical association in these depicted examples. Forexample, a first component, layer 212, may be considered to beassociated with a second component, first face sheet 204, by beingsecured to the second component, bonded to the second component, mountedto the second component, welded to the second component, fastened to thesecond component, and/or connected to the second component in some othersuitable manner. The first component also may be connected to the secondcomponent using a third component. The first component may also beconsidered to be associated with the second component by being formed aspart of and/or an extension of the second component.

Number of structures 210 in noise reduction system 211 has aconfiguration that reduces a speed of waves propagating throughcomposite panel 202 such that noise radiating from composite panel 202is reduced. In particular, number of structures 210 may have a mass witha configuration to reduce the speed of waves propagating throughcomposite panel 202.

In these illustrative examples, first face sheet 204 and second facesheet 206 may be comprised of various types of materials. Thesematerials may include, for example, without limitation, glass epoxy,carbon or graphite epoxy, and other suitable materials.

Core 208 is less dense than first face sheet 204 and second face sheet206. In these illustrative examples, core 208 may be solid or may havevoids in the structure. For example, the voids may take the form ofchannels in a honeycomb structure. In other illustrative examples, core208 may have voids that are closed rather than channels in ahoneycomb-type structure. Of course, other types of structures may beused, depending on the particular implementation. Core 208 may becomprised of various materials, such as, for example, withoutlimitation, paper, plastic, foam, a meta aramid material, a para aramidmaterial, and other suitable types of materials.

Turning now to FIG. 3, a cross-sectional view of a composite panel isdepicted in accordance with an illustrative embodiment. In thisillustrative example, a cross-sectional view of composite panel 202taken along lines 3-3 in FIG. 2 is depicted in accordance with anillustrative embodiment.

In this illustrative example, waves may travel through composite panel202. In these illustrative examples, the waves may include shear wavesand longitudinal waves. In this illustration, input 300 to compositepanel 202 may cause shear wave 304. Input 300 may be, for example, avibration and/or other movement.

As depicted, shear wave 304 travels through composite panel 202 and, inparticular, through core 208. Shear wave 304 is a wave in which elasticdeformation is substantially perpendicular to the direction of motion ofshear wave 304. In other words, elastic deformation may occur in thedirection of arrow 302 in this illustrative example.

As shear wave 304 travels through composite panel 202, sound 306 may beradiated from first face sheet 204. Sound 306 may be reduced through theuse of layer 212 in number of structures 210 in noise reduction system211 in these illustrative examples.

In this example, layer 212 adds mass that may reduce the speed of shearwave 304 as shear wave 304 travels through composite panel 202. Inparticular, the selection of the mass for layer 212 is made to reducethe speed of shear wave 304 to a speed that is less than the speed ofsound. In this illustrative example, shear wave 304 may be reducedthrough shear wave 304 traveling through core 208.

Turning next to FIG. 4, an illustration of a composite structure with anoise reduction system is depicted in accordance with an illustrativeembodiment. As shown, an isometric view of composite structure 400 isdepicted in accordance with an illustrative embodiment. In thisillustrative example, composite structure 400 is an example of acomposite structure that may be used in aircraft 100 in FIG. 1.

In particular, composite structure 400 takes the form of composite panel402. As illustrated, composite panel 402 has first face sheet 404,second face sheet 406, and core 408. Core 408 is located between firstface sheet 404 and second face sheet 406. Additionally, composite panel402 is associated with noise reduction system 409.

In this illustrative example, noise reduction system 409 comprisesnumber of structures 410. As depicted, number of structures 410 islocated on outer surface 412 of first face sheet 404. Outer surface 412is a surface exposed and not in contact with core 408 in theseillustrative examples.

Number of structures 410 takes the form of elongate members 414. Forexample, elongate member 416 in elongate members 414 is located on outersurface 412 of first face sheet 404. Elongate member 416 extends fromside 418 of composite panel 402 to side 420 of composite panel 402.

Turning now to FIG. 5, an illustration of a cross-sectional view of acomposite panel is depicted in accordance with an illustrativeembodiment. In this illustrative example, the cross-sectional view ofcomposite panel 402 is taken along lines 5-5 in FIG. 4.

In this illustrative example, elongate member 416 has a cross section inthe shape of a square. Of course, elongate member 416 may have othershapes, depending on the particular implementation. For example, thecross section may be rectangular, trapezoidal, oval, circular, or someother suitable shape, depending on the particular implementation.

As can be seen in this illustrative example, elongate members 414 aresubstantially evenly spaced from each other and extend substantiallyparallel to each other. The spacing between elongate members 414, crosssection shape, and other parameters for elongate members 414 is selectedto reduce noise that radiates from composite panel 402. The amount ofadded weight from elongate members 414 may also be a factor. Balancingbetween the weight of composite panel 402 and a reduction in noiseradiating from composite panel 402 may be performed.

With reference now to FIG. 6, an illustration of a composite structurewith a noise reduction system is depicted in accordance with anillustrative embodiment. Composite structure 600 is another example of acomposite structure that may be used in components in aircraft 100 inFIG. 1.

In this illustrative example, composite structure 600 takes the form ofcomposite panel 602. Composite panel 602 has first face sheet 604,second face sheet 606, and core 608. Core 608 is located between firstface sheet 604 and second face sheet 606.

In this illustrative example, noise reduction system 610 is located onouter surface 612 of first face sheet 604. Noise reduction system 610comprises number of structures 613. In these illustrative examples,number of structures 613 takes the form of patches 614. In thisillustrative example, patch 616 in patches 614 has the shape of a cube.Other shapes that may be used for patches 614 may include a sphere, apyramid, a cuboid, a cylinder, or some other suitable shape. Of course,patch 616 may have other shapes, depending on the particularimplementation.

With reference now to FIG. 7, a cross-sectional view of a compositestructure with a noise reduction system is depicted in accordance withan illustrative embodiment. A cross-sectional view of composite panel602 is seen taken along lines 7-7 in FIG. 6 in this illustrativeexample.

With reference now to FIG. 8, an illustration of a composite structurewith a noise reduction system is depicted in accordance with anillustrative embodiment. In this illustrative example, compositestructure 800 is another example of a composite structure that may beused in aircraft 100.

Composite structure 800 is composite panel 802 with first face sheet804, second face sheet 806, and core 808 located between the facesheets. In this illustrative example, noise reduction system 810 islocated inside of composite panel 802 rather than on outer surface 812of first face sheet 804. In this illustrative example, core 808 isattached to outer surface 812 of first face sheet 804.

As depicted, noise reduction system 810 comprises number of structures814. Number of structures 814 is configured to reduce a speed of wavestraveling through composite panel 802. In this illustrative example,number of structures 814 comprises voids 816 and elongate members 818located in voids 816 inside of composite panel 802. These components areshown in phantom in this illustrative example. In these illustrativeexamples, structures take the form of elongate members 818.

With reference now to FIG. 9, a cross-sectional view of a compositepanel is depicted in accordance with an illustrative embodiment. In thisillustrative example, a cross-sectional view of composite panel 802 isseen taken along lines 9-9 in FIG. 8.

As can be seen in this view, voids 816 are formed within core 808. Voids816 are configured such that gaps 903 are present between elongatemembers 818 and core 808. In other words, elongate members 818 do nottouch core 808 in these illustrative examples.

For example, elongate member 900 in elongate members 818 is locatedwithin void 902 in voids 816. As can be seen, gap 904 is present betweenelongate member 900 and walls 906 of core 808.

Turning next to FIG. 10, an illustration of a composite structure isdepicted in accordance with an illustrative embodiment. In thisillustrative example, composite structure 1000 takes the form ofcomposite panel 1002 and is another example of a composite structurethat may be used within aircraft 100.

As depicted, composite panel 1002 includes first face sheet 1004, secondface sheet 1006, and core 1008 located between first face sheet 1004 andsecond face sheet 1006. Noise reduction system 1010 is associated withouter surface 1012 of first face sheet 1004.

As can be seen in this illustrative example, noise reduction system 1010has number of structures 1013. As depicted, number of structures 1013comprises third face sheet 1014, patches 1016, voids 1018, and core1020. Number of structures 1013 has a mass configured to reduce a speedof waves traveling through composite panel 1002. As depicted, patches1016 are located under third face sheet 1014 in voids 1018 formed incore 1020 of noise reduction system 1010. Patches 1016 and voids 1018are shown in phantom in core 1020 in this depicted example.

Core 1020 is a second core and is located on outer surface 1012 of firstface sheet 1004. As a result, core 1020 is located between third facesheet 1014 of noise reduction system 1010 and first face sheet 1004 ofcomposite panel 1002.

Turning next to FIG. 11, an illustration of a cross-sectional view of acomposite structure is depicted in accordance with an illustrativeembodiment. In this illustrative example, a cross-sectional view ofcomposite panel 1002 taken along lines 11-11 in FIG. 10 is depicted.

As can be seen, voids 1018 provide gaps 1100 between patches 1016 andcore 1020. For example, patch 1102 is attached to inner surface 1104 ofthird face sheet 1014. Void 1106 in voids 1018 provides gap 1108 betweenwalls 1110 of core 1008 and patch 1102. In these illustrative examples,patch 1102 takes the form of a cylinder. Of course, other shapes may beused. For example, a sphere, a cube, and other suitable shapes may beused. Further, a mix of shapes may be used in the illustrative examples.

In these illustrative examples, core 1020 and core 1008 may be made ofthe same type of material or different types of materials, depending onthe particular implementation. The material selected for core 1020 maybe based on the speed of waves in core 1020 that will slow down thespeed of waves in core 1008. In particular, the waves are shear waves.The material selected may have a shear modulus that is lower than theshear modulus of core 1008. The difference in the shear modulus isselected to result in a desired reduction in the speed of shear waves incore 1008.

The illustration of noise reduction systems used with compositestructures in the form of composite panels in FIGS. 2-11 are not meantto imply limitations to the manner in which different illustrativeembodiments may be implemented. Other components may be used in additionto and/or in place of the ones illustrated. Also, other configurationsmay be present.

For example, structures for reducing noise may be placed on both facesheets instead of just one face sheet as depicted in the illustrativeexamples. In still other illustrative examples, structures may belocated both on the outside and on the inside of the composite panel.

In still other illustrative examples, the noise reduction systems may beused with other types of composite structures. For example, the noisereduction systems illustrated in the figures may be used with compositeskin-stringer-structures and other suitable structures.

Turning next to FIG. 12, an illustration of a design environment fordesigning noise reduction systems for composite structures is depictedin accordance with an illustrative embodiment. In this illustrativeexample, design environment 1200 includes noise reduction systemdesigner 1202, which is used to design noise reduction systems. Thesenoise reduction systems may be used with composite structures, such asthose found in aircraft 100 in FIG. 1.

As depicted, noise reduction system designer 1202 may be implementedusing hardware, software, or a combination of the two. In theseillustrative examples, noise reduction system designer 1202 may beimplemented in computer system 1204. Computer system 1204 is one or morecomputers in these illustrative examples. When more than one computer ispresent in computer system 1204, those computers may be in communicationwith each other using a local area network, the Internet, or some othersuitable type of communications media.

In this illustrative example, noise reduction system designer 1202 mayreceive composite structure design 1206. Composite structure design 1206is for composite structure 1207 in this illustrative example. Compositestructure 1207 may be, for example, composite panel 1208. Compositestructure design 1206 may be, for example, an input to produce noisereduction system design 1209.

In this illustrative example, noise reduction system designer 1202analyzes composite structure design 1206 to generate noise reductionsystem design 1209 for noise reduction system 1211. Noise reductionsystem design 1209 may include just the noise reduction system or alsomay include the composite structure in composite structure design 1206within the design.

Noise reduction system designer 1202 takes into account parameters 1210in composite structure design 1206. Parameters 1210 are for components1212 that may be part of the composite structure. In these illustrativeexamples, components 1212 for composite structure design 1206 includefirst face sheet 1218, second face sheet 1220, and core 1222.

Parameters 1210 may include various parameters, such as, for example,dimensions, materials, and other suitable parameters. Parameters 1210may be used to simulate waves that may travel through a compositestructure, such as a composite panel.

With parameters 1210, noise reduction system designer 1202 generatesparameters 1214 for noise reduction system design 1209. In theseillustrative examples, parameters 1214 are for components 1216 in noisereduction system design 1209.

In generating noise reduction system design 1209 for noise reductionsystem 1211, the speed of shear waves in core 1222 is taken intoaccount. The speed of shear waves in a core material is defined asfollows:

$C_{mc} = \lbrack \frac{G_{c}}{\rho_{c}} \rbrack^{1/2}$where C_(mc) is the speed of shear waves in the core material, G_(c) isthe shear modulus, and ρ_(c) is the density of the core.

In these illustrative examples, noise reduction system designer 1202takes into account that the mass of first face sheet 1218 and secondface sheet 1220 may change the speed of shear waves through thecomposite panel. The speed of shear waves through the composite panel isas follows:

$C_{s} = \lbrack {( \frac{1}{1 + {2\rho_{f}{t_{f}/\rho_{c}}t_{c}}} )\frac{G_{c}}{\rho_{c}}} \rbrack^{1/2}$where C_(s) is the speed of shear waves through the composite panel,G_(c) is the shear modulus, ρ_(c) is the density of the core, and t_(c)is the thickness of the core, ρ_(f) is the density of the face sheets,and t_(f) is the thickness of the face sheets.

The different illustrative embodiments recognize and take into accountthat at low frequencies, a composite panel having a sandwich structuremay be dominated by bending of the entire structure. In theseillustrative examples, low frequencies are frequencies from about 100 Hzto about 500 Hz. At very high frequencies, the composite panel has aresponse that is mostly controlled by the bending characteristics of theface sheets. In these illustrative examples, very high frequencies arefrequencies above about 10,000 Hz. The different illustrativeembodiments also recognize and take into account that the shear waves inthe composite panel govern the behavior of the composite panel in themid-frequency region. The mid-frequency range is from about 500 Hz toabout 10,000 Hz in these examples.

The different illustrative embodiments recognize and take into accountthat these modes may exist whether the core is a honeycomb core or asolid core in a composite panel. The different illustrative embodimentsrecognize and take into account that in the mid-frequency region, amajority of the vibration energy may be carried in the core in shearwaves traveling through the core. At low frequencies, most of the energymay be carried though the face sheets. Further, the differentillustrative embodiments recognize and take into account that at highfrequencies, the bending modes of the face sheets may dominate thevibration and noise radiation.

As a result, noise reduction system designer 1202 generates noisereduction system design 1209 for noise reduction system 1211 in a mannerthat reduces the speed of waves traveling though a composite structure.In particular, noise reduction system designer 1202 may generate noisereduction system design 1209 to cause waves traveling through acomposite structure using composite structure design 1206 to be reducedto a speed that is less than the speed of sound.

In these illustrative examples, noise reduction system designer 1202generates noise reduction system design 1209 for noise reduction system1211 in a manner that increases the mass of at least one of first facesheet 1218, second face sheet 1220, or both.

In these illustrative examples, by increasing the mass, the shear wavespeed may be shown as follows:

$C_{s} = \lbrack {( \frac{1}{1 + {{( {{2\rho_{f}t_{f}} + {\rho_{add}t_{add}}} )/\rho_{c}}t_{c}}} )\frac{G_{c}}{\rho_{c}}} \rbrack^{1/2}$where C_(s) is the speed of shear waves, G_(c) is the shear modulus,ρ_(c) is the density of the core, t_(c) is the thickness of the core,ρ_(f) is the density of the face sheets, t_(f) is the thickness of theface sheets, ρ_(add) is the density of the added mass to a face sheet,and t_(add) is the added thickness to a face sheet.

In these illustrative examples, noise reduction system designer 1202 maygenerate components 1216 for number of structures 1223 in noisereduction system 1211, such as elongate members 1224, patches 1226,layers 1228, and other suitable forms in which additional mass may beadded to first face sheet 1218, second face sheet 1220, or both. Inthese illustrative examples, components 1216 may be attached to firstface sheet 1218, second face sheet 1220, or both, depending on theparticular implementation.

In these illustrative examples, voids 1230 may be components incomponents 1216 in noise reduction system design 1209. Voids 1230 may becavities inside of the composite structure. Voids 1230 may be cavitiesin which elongate members 1224, patches 1226, or other structures may belocated. Voids 1230 may provide a gap between these components and core1222. Depending on the particular implementation, voids 1230 may beformed in core 1222. Voids 1230 may be used when elongate members 1224or patches 1226 are located inside of the composite structure ratherthan on the surface of the composite structure.

Additionally, noise reduction system designer 1202 also generatesparameters 1214 for components 1216. These parameters may include, forexample, without limitation, shape, an amount of mass, location, andother suitable parameters for the different components. These parametersare selected to reduce the speed of waves traveling through a compositestructure. The parameters also may be selected to reduce energy in theface sheets.

In this manner, components 1216 may reduce the speed of a wave.Components 1216 do not need to absorb vibration energy or be tuned tospecific temperatures in the illustrative examples. Further, thesecomponents do not need to absorb acoustic energy like fiberglassblankets. They also do not move like acoustic and/or vibrationresonators to absorb sound. Further, components 1216 are designed tomaintain the structural functions of the composite structures to whichthey are associated.

These designs may be more lightweight and efficient in reducing noise ascompared to currently used noise reduction systems. Further, the noisereduction systems are insensitive to temperature, because the propertiesof components 1216, such as elongate members, are not temperaturedependent.

Further, these noise reduction systems may be added on or integratedinto existing components rather than functioning as separate systemsfrom the composite structures from which they reduce noise.

With reference now to FIG. 13, an illustration of a flowchart of aprocess for reducing noise is depicted in accordance with anillustrative embodiment. The process illustrated in FIG. 13 may beimplemented in aircraft 100 in FIG. 1. In particular, the process may beimplemented in composite structures used in aircraft 100. Still moreparticularly, this process may be applied to a composite panel. Thenumber of structures has a mass with a configuration to reduce a speedof the waves propagating through a composite panel such that noiseradiating from the composite panel is reduced. In these illustrativeexamples, these waves may take the form of shear waves.

The process begins by causing waves to propagate through a compositepanel (operation 1300). The process then reduces the speed of the wavespropagating through the composite panel with the number of structuresassociated with a first face sheet in the composite panel (operation1302), with the process terminating thereafter.

Reducing the speed of waves propagating through the composite panel mayreduce the amount of noise radiated from the composite panel. Inparticular, the amount of noise radiated may be reduced when the speedof the waves is reduced to a speed less than the speed of sound.

The flowchart and block diagrams in the different depicted embodimentsillustrate the architecture, functionality, and operation of somepossible implementations of apparatuses and methods in an illustrativeembodiment. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, function, and/or a portion ofan operation or step. For example, one or more of the blocks may beimplemented as program code, in hardware, or a combination of theprogram code and hardware. When implemented in hardware, the hardwaremay, for example, take the form of integrated circuits that aremanufactured or configured to perform one or more operations in theflowchart or block diagrams.

In some alternative implementations of an illustrative embodiment, thefunction or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Turning now to FIG. 14, an illustration of a graph of noise reductionresults is depicted in accordance with an illustrative embodiment. Inthis illustrative example, graph 1400 illustrates transmission lossesfor different noise reduction systems in accordance with an illustrativeembodiment.

X-axis 1402 illustrates frequency in Hertz. Y-axis 1404 illustratessound transmission loss in decibels. In this illustrative example, graph1400 includes line 1406, line 1408, line 1410, line 1412, line 1414, andline 1416.

Line 1406 illustrates transmission loss through a composite panelwithout the use of a noise reduction system in accordance with anillustrative embodiment. Line 1408, line 1410, line 1412, line 1414, andline 1416 illustrate noise reduction systems in which masses are addedin the form of elongate members to the surface of a face sheet. As canbe seen, the addition of elongate members with additional mass increasesthe transmission loss of a composite panel.

Turning now to FIG. 15, an illustration of a data processing system isdepicted in accordance with an illustrative embodiment. Data processingsystem 1500 may be used to implement one or more computers in computersystem 1204 in FIG. 12. In this illustrative example, data processingsystem 1500 includes communications framework 1502, which providescommunications between processor unit 1504, memory 1506, persistentstorage 1508, communications unit 1510, input/output (I/O) unit 1512,and display 1514. In this example, communications framework 1502 maytake the form of a bus system.

Processor unit 1504 serves to execute instructions for software that maybe loaded into memory 1506. Processor unit 1504 may be a number ofprocessors, a multi-processor core, or some other type of processor,depending on the particular implementation.

Memory 1506 and persistent storage 1508 are examples of storage devices1516. A storage device is any piece of hardware that is capable ofstoring information, such as, for example, without limitation, data,program code in functional form, and/or other suitable informationeither on a temporary basis and/or a permanent basis. Storage devices1516 may also be referred to as computer readable storage devices inthese illustrative examples. Memory 1506, in these examples, may be, forexample, a random access memory or any other suitable volatile ornon-volatile storage device. Persistent storage 1508 may take variousforms, depending on the particular implementation.

For example, persistent storage 1508 may contain one or more componentsor devices. For example, persistent storage 1508 may be a hard drive, aflash memory, a rewritable optical disk, a rewritable magnetic tape, orsome combination of the above.

Communications unit 1510, in these illustrative examples, provides forcommunications with other data processing systems or devices. In theseillustrative examples, communications unit 1510 is a network interfacecard.

Input/output unit 1512 allows for input and output of data with otherdevices that may be connected to data processing system 1500. Forexample, input/output unit 1512 may provide a connection for user inputthrough a keyboard, a mouse, and/or some other suitable input device.Further, input/output unit 1512 may send output to a printer. Display1514 provides a mechanism to display information to a user.

Instructions for the operating system, applications, and/or programs maybe located in storage devices 1516, which are in communication withprocessor unit 1504 through communications framework 1502. The processesof the different embodiments may be performed by processor unit 1504using computer-implemented instructions, which may be located in amemory, such as memory 1506.

These instructions are referred to as program code, computer usableprogram code, or computer readable program code that may be read andexecuted by a processor in processor unit 1504. The program code in thedifferent embodiments may be embodied on different physical or computerreadable storage media, such as memory 1506 or persistent storage 1508.

Program code 1518 is located in a functional form on computer readablemedia 1520 that is selectively removable and may be loaded onto ortransferred to data processing system 1500 for execution by processorunit 1504. Program code 1518 and computer readable media 1520 formcomputer program product 1522 in these illustrative examples. In oneexample, computer readable media 1520 may be computer readable storagemedia 1524 or computer readable signal media 1526.

In these illustrative examples, computer readable storage media 1524 isa physical or tangible storage device used to store program code 1518rather than a medium that propagates or transmits program code 1518.

Alternatively, program code 1518 may be transferred to data processingsystem 1500 using computer readable signal media 1526. Computer readablesignal media 1526 may be, for example, a propagated data signalcontaining program code 1518. For example, computer readable signalmedia 1526 may be an electromagnetic signal, an optical signal, and/orany other suitable type of signal.

The different components illustrated for data processing system 1500 arenot meant to provide architectural limitations to the manner in whichdifferent embodiments may be implemented. The different illustrativeembodiments may be implemented in a data processing system includingcomponents in addition to and/or in place of those illustrated for dataprocessing system 1500. Other components shown in FIG. 15 can be variedfrom the illustrative examples shown. The different embodiments may beimplemented using any hardware device or system capable of runningprogram code 1518.

Illustrative embodiments of the disclosure may be described in thecontext of aircraft manufacturing and service method 1600 as shown inFIG. 16 and aircraft 1700 as shown in FIG. 17. Turning first to FIG. 16,an illustration of an aircraft manufacturing and service method isdepicted in accordance with an illustrative embodiment. Duringpre-production, aircraft manufacturing and service method 1600 mayinclude specification and design 1602 of aircraft 1700 in FIG. 17 andmaterial procurement 1604.

During production, component and subassembly manufacturing 1606 andsystem integration 1608 of aircraft 1700 takes place. Thereafter,aircraft 1700 may go through certification and delivery 1610 in order tobe placed in service 1612. While in service 1612 by a customer, aircraft1700 is scheduled for routine maintenance and service 1614, which mayinclude modification, reconfiguration, refurbishment, and othermaintenance or service.

Each of the processes of aircraft manufacturing and service method 1600may be performed or carried out by a system integrator, a third party,and/or an operator. In these examples, the operator may be a customer.For the purposes of this description, a system integrator may include,without limitation, any number of aircraft manufacturers andmajor-system subcontractors; a third party may include, withoutlimitation, any number of vendors, subcontractors, and suppliers; and anoperator may be an airline, a leasing company, a military entity, aservice organization, and so on.

With reference now to FIG. 17, an illustration of an aircraft isdepicted in which an illustrative embodiment may be implemented. In thisexample, aircraft 1700 is produced by aircraft manufacturing and servicemethod 1600 in FIG. 16 and may include airframe 1702 with plurality ofsystems 1704 and interior 1706. Examples of systems 1704 include one ormore of propulsion system 1708, electrical system 1710, hydraulic system1712, and environmental system 1714. Any number of other systems may beincluded. Although an aerospace example is shown, different illustrativeembodiments may be applied to other industries, such as the automotiveindustry.

Apparatuses and methods embodied herein may be employed during at leastone of the stages of aircraft manufacturing and service method 1600 inFIG. 16. In one illustrative example, components or subassembliesproduced in component and subassembly manufacturing 1606 in FIG. 16 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while aircraft 1700 is in service 1612 in FIG.16.

As yet another example, one or more apparatus embodiments, methodembodiments, or a combination thereof may be utilized during productionstages, such as component and subassembly manufacturing 1606 and systemintegration 1608 in FIG. 16. For example, a composite panel or othercomposite structure may be manufactured with a noise reduction system inaccordance with an illustrative embodiment. One or more apparatusembodiments, method embodiments, or a combination thereof may beutilized while aircraft 1700 is in service 1612 and/or duringmaintenance and service 1614 in FIG. 16. For example, a noise reductionsystem may be added to existing composite structures or a new compositestructure may be manufactured with the noise reduction system duringmaintenance and service 1614. The use of a number of the differentillustrative embodiments may substantially expedite the assembly ofand/or reduce the cost of aircraft 1700.

In addition, although the illustrative examples have been depicted foruse in reducing noise in an aircraft, one or more illustrativeembodiments may be applied to other types of platforms. For example, oneor more illustrative embodiments may be implemented in a platformselected from one of a mobile platform, a stationary platform, aland-based structure, an aquatic-based structure, a space-basedstructure, and other suitable types of structures. For example, thedifferent illustrative embodiments may also be used in other vehicles,such as automobiles, surface ships, submarines, spacecraft, trains,personnel carrier, tanks, and other suitable vehicles. Further, one ormore illustrative embodiments may also be used with machinery,buildings, homes, space stations, satellites, power plants, bridges,dams, manufacturing facilities, and other suitable locations. Forexample, an illustrative embodiment may be used in walls, ceilings, andother components of an office or home that may be close to noisesources, such as an airport, a manufacturing facility, or some othernoise source.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different features as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. An apparatus comprising: a composite panel havinga first face sheet, a second face sheet, and a core located between thefirst face sheet and the second face sheet; and a number of structuresassociated with the first face sheet, the number of structures having amass with a configuration to reduce a speed of waves propagating in thecomposite panel such that noise radiating from the composite panel isreduced, the number of structures comprising a number of patchesattached to an inner surface of the first face sheet, the core includinga number of voids, the number of patches located in the number of voids,and the number of voids and the number of patches configured to providegaps between the number of patches and the core.
 2. The apparatus ofclaim 1, wherein the number of structures is configured to reduce thespeed of the waves to less than about a speed of sound.
 3. The apparatusof claim 1, wherein the core comprises a honeycomb.
 4. The apparatus ofclaim 1, wherein the patches comprise elongate members.
 5. The apparatusof claim 1, wherein the patches comprise a shape selected from one of acube, a cylinder, a sphere, a pyramid, or a cuboid.
 6. The apparatus ofclaim 1, wherein the composite panel is disposed in one of a wall, aceiling, or a floor, of an aircraft.
 7. The apparatus of claim 1,wherein the number of voids are closed with respect to the core.
 8. Theapparatus of claim 1, wherein the number of voids comprise a number ofchannels in a honeycomb structure of the core.
 9. The apparatus of claim1, wherein the core comprises a material selected from one of paper,plastic, foam, a meta aramid material, and a para aramid material.
 10. Amethod for reducing noise radiation from a composite panel, the methodcomprising: causing waves to propagate through the composite panelcomprising a first face sheet, a second face sheet, and a core locatedbetween the first face sheet and the second face sheet; and reducing aspeed of the waves propagating through the composite panel with a numberof structures associated with the first face sheet, the number ofstructures having a mass with a configuration to reduce the speed of thewaves propagating in the composite panel such that the noise radiatingfrom the composite panel is reduced, the number of structures comprisinga number of elongate members having the mass, the number of elongatemembers attached to an inner surface of the first face sheet and furthercomprising a number of voids in the core, the number of elongate memberslocated in the number of voids in the core and the number of voids andnumber of elongate members configured to provide a number of gapsbetween the number of elongate members and the core.
 11. The method ofclaim 10, wherein a second number of structures is associated with thesecond face sheet.
 12. The method of claim 10, wherein the number ofstructures reduces the speed of the waves to less than about a speed ofsound.
 13. The method of claim 10 further comprising installing thecomposite panel in an aircraft.
 14. The method of claim 10 furthercomprising reducing the speed of a shear wave through the compositepanel.